WO2020080245A1

WO2020080245A1 - Negative electrode for lithium ion secondary battery, and lithium ion secondary battery

Info

Publication number: WO2020080245A1
Application number: PCT/JP2019/039972
Authority: WO
Inventors: 永田　佳秀; 直樹越谷
Original assignee: 株式会社村田製作所
Priority date: 2018-10-17
Filing date: 2019-10-10
Publication date: 2020-04-23
Also published as: EP3869586A4; US20210242489A1; EP3869586A1; CN112805849B; JPWO2020080245A1; CN112805849A; JP7074203B2

Abstract

This lithium ion secondary battery comprises: a positive electrode; a negative electrode comprising a negative electrode active material layer that has a plurality of pores, the negative electrode active material layer including a plurality of first negative electrode active material particles and a plurality of second negative electrode active material particles, each of the plurality of first negative electrode active material particles including a plurality of carbon-containing particles and a plurality of silicon-containing particles in an ion transfer substance, each of the second negative electrode active material particles contains a carbon-containing material, and the range of pore diameters at which a peak is shown in the volumetric fraction of the amount of mercury intruding into the plurality of pores is 1-3 μm; and a liquid electrolyte.

Description

Negative electrode for lithium-ion secondary battery and lithium-ion secondary battery

The present technology relates to a negative electrode used in a lithium ion secondary battery and a lithium ion secondary battery using the negative electrode.

Due to the widespread use of various electronic devices such as mobile phones, the development of lithium-ion secondary batteries that are compact and lightweight and that can obtain high energy density as a power source is under way.

This lithium-ion secondary battery is equipped with an electrolyte solution as well as a positive electrode and a negative electrode. Since the configuration of the negative electrode has a great influence on the battery characteristics, various studies have been made on the configuration of the negative electrode. Specifically, in order to obtain excellent cycle characteristics and the like, a binder that is a fluororesin is used together with the negative electrode active material. In this negative electrode active material, a polymer compound having a carboxyl group and metal oxide particles are attached to the surface of a composite material (carbon material, graphite material and metal material) (for example, see Patent Document 1).

JP, 2013-157339, A

Electronic devices equipped with lithium-ion secondary batteries are becoming increasingly sophisticated and multifunctional, so the frequency of use of the electronic devices is increasing and the environment in which the electronic devices are used is expanding. . Therefore, there is still room for improvement in the battery characteristics of the lithium ion secondary battery.

The present technology has been made in view of such problems, and an object thereof is to provide a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery that can obtain excellent battery characteristics.

A negative electrode for a lithium-ion secondary battery according to an embodiment of the present technology includes a positive electrode and a negative electrode active material layer having a plurality of pores, and the negative electrode active material layer has a plurality of first negative electrode active material particles and a plurality of first negative electrode active material particles. 2 negative electrode active material particles, each of the plurality of first negative electrode active material particles includes a plurality of carbon-containing particles and a plurality of silicon-containing particles in the ion conductive material, and each of the second negative electrode active material particles. A negative electrode that contains a carbon-containing material and has a pore diameter range in which the volume fraction of mercury intrusion into a plurality of pores shows a peak is 1 μm or more and 3 μm or less, and an electrolyte solution.

A lithium ion secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolytic solution, and the negative electrode has the same configuration as the above-described negative electrode for a lithium ion secondary battery according to an embodiment of the present technology. I have.

The above-mentioned “volume fraction of the amount of mercury infiltrating into a plurality of pores” is measured using the mercury porosimetry (mercury porosimeter). However, the amount of mercury penetration is measured when the surface tension of mercury is 485 mN / m and the contact angle is 130 °, and the relationship between the pore diameter and the pressure of a plurality of pores is approximately 180 / pressure = pore diameter. Value.

Along with this, "the range of the pore diameter at which the volume fraction of the amount of infiltration of mercury into a plurality of pores shows a peak is 1 μm or more and 3 μm or less" is the measurement result of the mercury porosimeter (the horizontal axis indicates the pore diameter (μm) and In the vertical axis of the volume fraction of mercury intrusion (%), when focusing on the range of the pore diameter on the horizontal axis of 1 μm to 3 μm, the volume fraction of mercury intrusion is an upward convex curve ( It means that the peaks are distributed so as to draw a peak, and the apex of the peak is located within the range where the pore diameter is 1 μm to 3 μm.

According to the negative electrode for a lithium ion secondary battery or the lithium ion secondary battery of the present technology, the plurality of first negative electrode active material particles and the plurality of second negative electrode active material particles in which the negative electrode active material layer having a plurality of pores is described above. And satisfying the above-mentioned conditions regarding the range of the pore diameter at which the volume fraction of the amount of mercury infiltrated into the plurality of pores shows a peak, excellent battery characteristics can be obtained.

The effect of the present technology is not necessarily limited to the effect described here, and may be any one of a series of effects related to the present technology described later.

It is a sectional view showing composition of a negative electrode for lithium ion rechargeable batteries of one embodiment of this art. It is sectional drawing which represents typically each structure of a 1st negative electrode active material particle and a 2nd negative electrode active material particle. It is a figure showing an example of the measurement result of a mercury porosimeter (a horizontal axis is a hole diameter (%) and a vertical axis is a volume fraction (%) of the amount of penetration of mercury). It is a sectional view showing composition of a lithium ion secondary battery (cylindrical type) of one embodiment of this art. It is sectional drawing which expands and represents the structure of the principal part of the lithium ion secondary battery shown in FIG. It is a perspective view showing composition of other lithium ion rechargeable batteries (laminate film type) of one embodiment of this art. FIG. 7 is a cross-sectional view showing an enlarged configuration of a main part of the lithium-ion secondary battery shown in FIG. 6.

Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The order of description is as follows.

1. Negative electrode for lithium-ion secondary battery 1-1. Configuration 1-2. Manufacturing method 1-3. Action and effect 2. Lithium ion secondary battery 2-1. Cylindrical type 2-1-1. Configuration 2-1-2. Operation 2-1-3. Manufacturing method 2-1-4. Action and effect 2-2. Laminated film type 2-2-1. Configuration 2-2-2. Operation 2-2-3. Manufacturing method 2-2-4. Action and effect 3. Modified example 4. Applications of lithium-ion secondary batteries

<1. Negative electrode for lithium-ion secondary battery>
First, a negative electrode for a lithium ion secondary battery (hereinafter, simply referred to as “negative electrode”) according to an embodiment of the present technology will be described.

The lithium-ion secondary battery in which the negative electrode described here is used is a secondary battery in which the battery capacity can be obtained by utilizing the occlusion / release of lithium, as described below.

<1-1. Composition>
FIG. 1 shows a cross-sectional structure of a negative electrode 10, which is an example of the negative electrode. FIG. 2 schematically shows respective cross-sectional configurations of the first negative electrode active material particles 100 and the second negative electrode active material particles 200. FIG. 3 shows an example of the measurement result of the mercury porosimeter. In FIG. 3, the horizontal axis represents the hole diameter (%), and the vertical axis represents the volume fraction (%) of the amount of infiltration of mercury.

The negative electrode 10 includes the negative electrode active material layer 2 as shown in FIG. More specifically, the negative electrode 10 includes, for example, the negative electrode current collector 1, and the above-described negative electrode active material layer 2 is provided on the negative electrode current collector 1. However, the negative electrode active material layer 2 may be provided on only one surface of the negative electrode current collector 1, or may be provided on both surfaces of the negative electrode current collector 1. In FIG. 1, for example, the case where the negative electrode active material layers 2 are provided on both surfaces of the negative electrode current collector 1 is shown.

[Negative electrode current collector]
The negative electrode current collector 1 contains a conductive material such as copper. The surface of the negative electrode current collector 1 is preferably roughened by an electrolytic method or the like. This is because the adhesion of the negative electrode active material layer 2 to the negative electrode current collector 1 is improved by utilizing the anchor effect.

[Negative electrode active material layer]
As shown in FIG. 2, the negative electrode active material layer 2 contains two types of particulate negative electrode active materials (a plurality of first negative electrode active material particles 100 and a plurality of second negative electrode active material particles 200). Therefore, the negative electrode active material layer 2 has a plurality of pores (voids). In FIG. 2, only one first negative electrode active material particle 100 is shown, and only one second negative electrode active material particle 200 is shown. However, the negative electrode active material layer 2 may further include any one kind or two or more kinds of other materials such as a negative electrode binder and a negative electrode conductive agent.

(Plurality of first negative electrode active material particles)
As shown in FIG. 2, the first negative electrode active material particles 100 include, in the ion conductive material 101, a plurality of carbon-containing particles 102 that occlude and release lithium and a plurality of silicon-containing particles 103 that occlude and release lithium. Is included.

That is, the first negative electrode active material particles 100 are composite particles in which a plurality of carbon-containing particles 102 and a plurality of silicon-containing particles 103 are contained (embedded) in the ion conductive material 101. However, some of the plurality of carbon-containing particles 102 may be partially exposed from the ion conductive material 101. The fact that the ion-conductive substance 101 may be partially exposed in this way is the same for some of the plurality of silicon-containing particles 103.

The average particle diameter (median diameter D50) of the plurality of first negative electrode active material particles 100 is not particularly limited, but is preferably 3.5 μm to 13.0 μm among them. This is because the average particle diameter of the plurality of first negative electrode active material particles 100 is optimized in relation to the average particle diameter (median diameter D50) of the plurality of second negative electrode active material particles 200. This facilitates controlling the distribution of the plurality of pores so that a predetermined condition, which will be described later, is satisfied with respect to the volume fraction of the infiltration amount of mercury with respect to the plurality of pores in the negative electrode active material layer 2.

(Ion conductive material)
The ion conductive material 101 is a material that improves the conductivity of lithium ions to facilitate the input and output of lithium ions in each of the carbon-containing particles 102 and the silicon-containing particles 103.

The ion conductive material 101 contains, for example, one kind or two or more kinds of an ion conductive polymer compound and a solid electrolyte. This is because sufficient ionic conductivity can be obtained inside the first negative electrode active material particles 100. Specifically, the ion conductive polymer compound is, for example, polyether, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polyacrylonitrile, polymethacrylonitrile, Polyvinylacetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, polyaniline, polypyrrole, polythiophene, polyacetylene, polyphenylene, polyparaphenylene, polyphenylenevinylene, polyoxadiazole, polyhexafluoropropylene and polyethylene carbonate, and the like. Polyethers are, for example, polyethylene oxide (PEO) and polypropylene oxide (PPO).

The ion-conductive polymer compound may be, for example, a derivative such as the above-mentioned polyether. Further, the ion-conductive polymer compound may be, for example, a homopolymer such as the above-mentioned polyether, or may be a copolymer of any two or more kinds of the polyether and the like. Among them, the ion conductive polymer compound is preferably polyethylene oxide. This is because high ionic conductivity can be obtained.

The ionic conductivity of the ionic conductive material 101 is not particularly limited, but is preferably 10 ⁻⁶ S / cm to 10 ⁻¹ S / cm. This is because it becomes easy for lithium ions to smoothly and stably input and output in each of the carbon-containing particles 102 and the silicon-containing particles 103.

The content of the ion conductive material 101 in the first negative electrode active material particles 100 is not particularly limited. Above all, the ratio of the weight of the ion conductive material 101 to the weight of the first negative electrode active material particles 100 (weight ratio R1) is preferably 1.0% by weight to 2.5% by weight. Since the amount of the ion conductive material 101 is optimized with respect to the respective amounts of the plurality of carbon-containing particles 102 and the plurality of silicon-containing particles 103, excellent ion conductivity can be obtained while ensuring a high energy density. Is.

(Multiple carbon-containing particles)
The carbon-containing particles 102 include any one kind or two or more kinds of carbon-containing materials as a negative electrode material that absorbs and releases lithium. The carbon-containing material is a general term for materials containing carbon as a constituent element. This is because the crystal structure of the carbon-containing material hardly changes during occlusion / release of lithium, so that a high energy density can be stably obtained. Further, the carbon-containing material also functions as a negative electrode conductive agent, so that the conductivity of the first negative electrode active material particles 100 is improved.

Specifically, the carbon-containing material is, for example, graphitizable carbon, non-graphitizable carbon and graphite. However, the interplanar spacing of the (002) plane for non-graphitizable carbon is, for example, 0.37 nm or more, and the interplanar spacing of the (002) plane for graphite is, for example, 0.34 nm or less.

More specifically, the carbon-containing material is, for example, pyrolytic carbon, coke, glassy carbon fiber, organic polymer compound fired body, activated carbon and carbon black. The cokes include, for example, pitch cokes, needle cokes and petroleum cokes. The organic polymer compound fired body is a fired product obtained by firing (carbonizing) a polymer compound such as a phenol resin and a furan resin at an arbitrary temperature. In addition, the carbon-containing material may be, for example, low crystalline carbon heat-treated at a temperature of about 1000 ° C. or lower, or amorphous carbon. The shape of the carbon material is, for example, fibrous, spherical, granular or scaly.

(Plurality of silicon-containing particles)
The silicon-containing particles 103 contain any one kind or two or more kinds of silicon-containing materials as a negative electrode material that absorbs and releases lithium. This silicon-containing material is a general term for materials containing silicon as a constituent element. This is because a high energy density can be obtained due to the excellent ability to store and release lithium.

This silicon-containing material is capable of forming an alloy with lithium, and may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more thereof, or one of them. A material containing one kind or two or more kinds of phases may be used. However, since the simple substance described here means a general simple substance, it may contain a trace amount of impurities. That is, the purity of the simple substance is not necessarily 100%.

The alloy of silicon is, for example, as a constituent element other than silicon, any one of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium, or Contains two or more types. The compound of silicon contains, for example, one or more of carbon and oxygen as constituent elements other than silicon. The silicon compound may include, for example, as a constituent element other than silicon, any one kind or two kinds or more of the series of constituent elements described for the alloy of silicon.

Specifically, silicon alloys and silicon compounds include, for example, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O and SiO _v (0 <v ≦ 2). However, the range of v may be 0.2 <v <1.4, for example.

The mixing ratio (weight ratio) of the plurality of carbon-containing particles 102 and the plurality of silicon-containing particles 103 is not particularly limited. Above all, the ratio (weight ratio R2) of the weight of the plurality of silicon-containing particles 103 to the total weight of the plurality of carbon-containing particles 102 and the weight of the plurality of silicon-containing particles 103 is 60.6% by weight to 85%. It is preferably 1.9% by weight. Since the amount of the plurality of silicon-containing particles 103 is optimized with respect to the amount of the plurality of carbon-containing particles 102, the expansion and contraction of the negative electrode active material layer 2 due to the presence of the silicon-containing material is suppressed, and the high energy density is achieved. Is obtained, and also excellent ion conductivity is obtained. The value of the weight ratio R2 is a value rounded off to the second decimal place.

(Plurality of second negative electrode active material particles)
As shown in FIG. 2, the second negative electrode active material particles 200 include any one kind or two or more kinds of carbon-containing materials. Details regarding the carbon-containing material are as described above. The kind of carbon-containing material contained in the second negative electrode active material particles 200 may be the same as the kind of carbon-containing material contained in the carbon-containing particles 102, or the kind of carbon-containing material contained in the carbon-containing particles 102. May be different.

The average particle diameter (median diameter D50) of the plurality of second negative electrode active material particles 200 is not particularly limited, but is preferably 7.0 μm to 20.0 μm among them. This is because the average particle diameter of the plurality of second negative electrode active material particles 200 is optimized in relation to the average particle diameter (median diameter D50) of the plurality of first negative electrode active material particles 100. Thereby, as described above, it becomes easy to control the distribution of the plurality of pores so that a predetermined condition is satisfied with respect to the volume fraction of the infiltration amount of mercury with respect to the plurality of pores in the negative electrode active material layer 2. .

The mixing ratio (weight ratio) of the plurality of first negative electrode active material particles 100 and the plurality of second negative electrode active material particles 200 is not particularly limited. Among them, the ratio of the weight of the plurality of first negative electrode active material particles 100 to the total weight of the plurality of first negative electrode active material particles 100 and the weight of the plurality of second negative electrode active material particles 200 (weight ratio R3) Is preferably 10.5% to 42.1% by weight. Since the amount of the plurality of first negative electrode active material particles 100 is optimized with respect to the amount of the plurality of second negative electrode active material particles 200, expansion and contraction of the negative electrode active material layer 2 due to the presence of the silicon-containing material is suppressed. This is because while high energy density is obtained, excellent ion conductivity is also obtained. The value of the weight ratio R3 is a value rounded off to the second decimal place.

(Physical properties of negative electrode active material layer)
Here, the plurality of pores included in the negative electrode active material layer 2 are distributed so as to satisfy a predetermined condition. Specifically, when the volume fraction of the amount of mercury infiltrated into a plurality of pores is measured, the pore diameter range in which the volume fraction of the amount of mercury intrusion shows a peak is 1 μm to 3 μm. Hereinafter, the conditions described here will be referred to as “pore size conditions”.

This "volume fraction of the amount of mercury infiltrating into multiple pores" is measured using the mercury porosimetry (mercury porosimeter) as described above. However, the amount of mercury penetration is measured when the surface tension of mercury is 485 mN / m and the contact angle is 130 °, and the relationship between the pore diameter and the pressure of a plurality of pores is approximately 180 / pressure = pore diameter. Value.

Along with this, "the range of the pore diameter at which the volume fraction of the infiltration amount of mercury into a plurality of pores shows a peak is 1 μm or more and 3 μm or less" means that the measurement result of the mercury porosimeter (the horizontal axis is In the pore size (μm) and the vertical axis, the volume fraction of mercury intrusion (%)), when focusing on the range of the pore diameter of 1 μm to 3 μm on the horizontal axis, the volume fraction of mercury intrusion is upward. A convex curve (peak) is drawn, and it means that the apex of the peak is located within the range where the pore diameter is 1 μm to 3 μm. The measurement result of the mercury porosimeter is data obtained by plotting the volume fraction of the infiltration amount of mercury against the pore diameter by measuring the intrusion amount of mercury into a plurality of pores while gradually increasing the pressure.

More specifically, if a peak is detected in the mercury porosimeter measurement results, check the pore diameter (corresponding pore diameter) corresponding to the peak apex. When the corresponding pore diameter is in the range of 1 μm to 3 μm, the pore diameter condition is satisfied. On the other hand, when the corresponding pore diameter is out of the range of 1 μm to 3 μm, the pore diameter condition is not satisfied.

As an example, assume that the mercury porosimeter measurement results shown in Fig. 3 were obtained. Here, when the peak P1 (solid line) is detected, the corresponding pore diameter is 2 μm, which satisfies the pore diameter condition. On the other hand, when the peak P2 (broken line) is detected, the corresponding pore diameter is 3.5 μm, which does not satisfy the pore diameter condition. In FIG. 3, the range of the pore diameter of 1 μm to 3 μm is shaded.

The corresponding pore diameter is 1 μm to 3 μm, and when the first negative electrode active material particles 100 include the ion conductive material 101, the amount of voids (void distribution) in the negative electrode active material layer 2 is optimized. Because. This improves the ion conductivity in each of the first negative electrode active material particles 100 and also improves the ion conductivity in the periphery of each of the first negative electrode active material particles 100. The sexuality is dramatically improved. Therefore, in the lithium ion secondary battery including the negative electrode 10 and the electrolytic solution, when the negative electrode 10 (a plurality of pores in the negative electrode active material layer 2) is impregnated with the electrolytic solution, the ions in the electrolytic solution are Since the transport efficiency is remarkably improved, it becomes easy for lithium ions to smoothly and stably input and output to and from the negative electrode 10.

In addition, the corresponding pore size changes each of the median diameter D50 of the plurality of first negative electrode active material particles 100 and the median diameter D50 of the plurality of second negative electrode active material particles 200 described above, that is, the ratio of the median diameters D50 of both. It can be adjusted to a desired value by changing it. This is because the distribution of voids in the negative electrode active material layer 2 changes, so the position of the peak detected in the measurement result of the mercury porosimeter changes.

When examining the corresponding pore size, for example, the negative electrode active material layer 2 is cut so as to have a size of 25 mm × 350 mm, and a mercury porosimeter (Autopore 9500 series) manufactured by Micromeritics is used.

(Other negative electrode active materials)
The negative electrode active material layer 2 includes the above-described two types of negative electrode active materials (the plurality of first negative electrode active material particles 100 and the plurality of second negative electrode active material particles 200), and further, among other negative electrode active materials. Any one type or two or more types may be included.

The other negative electrode active material is, for example, a metal-based material, and the metal-based material is a general term for materials containing any one or more of metal elements and metalloid elements as constituent elements. This is because a high energy density can be obtained.

The metal-based material may be a simple substance, an alloy, a compound, a mixture of two or more kinds thereof, or a material containing one kind or two or more kinds of phases thereof. However, the alloy includes not only a material composed of two or more kinds of metal elements but also a material containing one kind or two or more kinds of metal elements and one kind or two or more kinds of metalloid elements. Further, the alloy may contain one kind or two or more kinds of non-metal elements. The structure of the metal-based material is, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a coexisting substance of two or more kinds thereof.

Each of the metal element and the metalloid element can form an alloy with lithium. Specifically, metal elements and metalloid elements are, for example, magnesium, boron, aluminum, gallium, indium, silicon, germanium, tin, lead, bismuth, cadmium, silver, zinc, hafnium, zirconium, yttrium, palladium and platinum. And so on.

Among them, silicon and tin are preferable, and silicon is more preferable. This is because the lithium storage and release capacity is excellent and a remarkably high energy density can be obtained.

Specifically, the metallic material may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a simple substance of tin, an alloy of tin, or a compound of tin. However, it may be a mixture of two or more kinds thereof, or a material containing one kind or two or more kinds of phases thereof.

The details regarding each of the alloy of silicon and the compound of silicon are as described above. The alloy of tin is, for example, as a constituent element other than tin, any one of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium, or Contains two or more types. The tin compound contains, for example, one or more of carbon and oxygen as constituent elements other than tin. The tin compound may include, for example, as a constituent element other than tin, one kind or two or more kinds of the series of constituent elements described for the alloy of tin. Specifically, the tin alloy and the tin compound are, for example, SnO _w (0 <w ≦ 2), SnSiO ₃ and Mg ₂ Sn.

(Negative electrode binder and negative electrode conductive agent)
The negative electrode binder contains, for example, synthetic rubber and a polymer compound. The synthetic rubber is, for example, styrene-butadiene rubber. The polymer compound is, for example, polyvinylidene fluoride, polyimide and aramid.

The negative electrode conductive agent contains a conductive material such as a carbon material. This carbon material is, for example, graphite, carbon black, acetylene black, Ketjen black, carbon nanotube, carbon nanofiber, or the like. However, the negative electrode conductive agent may be a metal material, a conductive polymer, or the like.

<1-2. Manufacturing method>
The negative electrode 10 is manufactured, for example, by the following procedure.

First, a mixture is obtained by mixing the ion conductive material 101, the plurality of carbon-containing particles 102, and the plurality of silicon-containing particles 103. Then, the mixture is put into a solvent, and then the solvent is stirred to prepare a mixed solution. The type of solvent is not particularly limited as long as it is any one type or two or more types of any solvent, and examples thereof include an aqueous solvent and an organic solvent capable of dissolving the ion conductive substance 101. The aqueous solvent is, for example, pure water, and the organic solvent is, for example, N-methyl-2-pyrrolidone. When stirring the solvent, for example, a stirring device such as a stirrer may be used. Then, after spraying the mixed solution using a spray drying device, the mixed solution is dried. Thereby, since the plurality of carbon-containing particles 102 and the plurality of silicon-containing particles 103 are contained in the ion conductive material 101, a plurality of first negative electrode active material particles 100 are obtained.

Subsequently, a plurality of first negative electrode active materials 100, a plurality of second negative electrode active material particles 200, and a negative electrode binder, a negative electrode conductive agent, and the like are mixed to form a negative electrode mixture. Then, the negative electrode mixture slurry is prepared by dispersing or dissolving the negative electrode mixture in an organic solvent or an aqueous solvent. Finally, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 1, and then the negative electrode mixture slurry is dried to form the negative electrode active material layer 2. After that, the negative electrode active material layer 2 may be compression molded using a roll press or the like. In this case, the negative electrode active material layer 2 may be heated or compression molding may be repeated a plurality of times.

With this, the negative electrode active material layers 2 are formed on both surfaces of the negative electrode current collector 1, so that the negative electrode 10 is completed.

<1-3. Action and effect>
According to this negative electrode 10, the negative electrode active material layer 2 having a plurality of pores has a plurality of first negative electrode active material particles 100 (ion conductive material 101, a plurality of carbon-containing particles 102 and a plurality of silicon-containing particles 103), and It includes a plurality of second negative electrode active material particles 200 and has a corresponding pore diameter of 1 μm to 3 μm.

In this case, as described above, since the ion conductivity is dramatically improved in the entire negative electrode active material layer 2, in the lithium ion secondary battery including the negative electrode 10 and the electrolytic solution, the ions in the electrolytic solution are Transport efficiency is significantly improved. Therefore, lithium ions can be smoothly and stably input to and output from the negative electrode 10, so that a secondary battery including the negative electrode 10 can have excellent battery characteristics.

In particular, if the ion conductive material 101 contains an ion conductive polymer compound or the like, sufficient ion conductivity can be obtained inside the first negative electrode active material particles 100, and a higher effect can be obtained.

When the ion conductivity of the ion-conductive substance 101 is 10 ⁻⁶ S / cm to 10 ⁻¹ S / cm, lithium ions are smoothly and stably input / output to / from each of the carbon-containing particles 102 and the silicon-containing particles 103. Since it is easier to do so, a higher effect can be obtained.

Further, if the weight ratio R1 is 1.0% by weight to 2.5% by weight, excellent ion conductivity can be obtained while ensuring a high energy density, so that a higher effect can be obtained.

When the weight ratio R2 is 60.6% by weight to 85.9% by weight, expansion and shrinkage of the negative electrode active material layer 2 due to the presence of the silicon-containing material are suppressed, and a high energy density is obtained and excellent. Also, high ionic conductivity can be obtained, so that a higher effect can be obtained.

Further, the median diameter D50 of the plurality of first negative electrode active material particles 100 is 3.5 μm to 13.0 μm, and the median diameter D50 of the plurality of second negative electrode active material particles 200 is 7.0 μm to 20.0 μm. In this case, the distribution of the plurality of pores is easily controlled so that a predetermined condition is satisfied with respect to the volume fraction of the infiltration amount of mercury, so that a higher effect can be obtained.

When the weight ratio R3 is 10.5% by weight to 42.1% by weight, the expansion and shrinkage of the negative electrode active material layer 2 due to the presence of the silicon-containing material is suppressed, a high energy density is obtained and excellent. Also, high ionic conductivity can be obtained, so that a higher effect can be obtained.

<2. Lithium-ion secondary battery>
Next, a lithium ion secondary battery according to an embodiment of the present technology using the above-described negative electrode 10 will be described.

The lithium-ion secondary battery described here includes a positive electrode 21 and a negative electrode 22, as described later. The lithium-ion secondary battery is, for example, a secondary battery in which the capacity of the negative electrode 22 is obtained by utilizing the occlusion and release of lithium.

In this lithium-ion secondary battery, for example, the charge capacity of the negative electrode 22 is larger than the discharge capacity of the positive electrode 21 in order to prevent unintentional deposition of lithium metal on the surface of the negative electrode 22 during charging. ing.

<2-1. Cylindrical type>
First, a cylindrical lithium ion secondary battery will be described as an example of the lithium ion secondary battery.

<2-1-1. Composition>
FIG. 4 shows a cross-sectional structure of the lithium-ion secondary battery, and FIG. 5 shows an enlarged cross-sectional structure of a main part (rolled electrode body 20) of the lithium-ion secondary battery shown in FIG. . However, in FIG. 5, only a part of the spirally wound electrode body 20 is shown.

In this lithium-ion secondary battery, for example, as shown in FIG. 4, a battery element (rolled electrode body 20) is housed inside a cylindrical battery can 11.

Specifically, the lithium ion secondary battery includes, for example, a pair of insulating

plates

12 and 13 and a wound electrode body 20 inside a battery can 11. The wound electrode body 20 is, for example, a structure in which a positive electrode 21 and a negative electrode 22 are stacked on each other via a separator 23, and then the positive electrode 21, a negative electrode 22 and a separator 23 are wound. The spirally wound electrode body 20 is impregnated with an electrolytic solution which is a liquid electrolyte.

The battery can 11 has, for example, a hollow cylindrical structure with one end closed and the other end open, and contains, for example, a metal material such as iron. However, the surface of the battery can 11 may be plated with a metal material such as nickel. Each of the insulating

plates

12 and 13 extends, for example, in a direction intersecting the winding peripheral surface of the wound electrode body 20 and is arranged so as to sandwich the wound electrode body 20 therebetween.

At the open end of the battery can 11, for example, the battery lid 14, the safety valve mechanism 15, and the PTC element 16 are caulked via the gasket 17, so that the open end of the battery can 11 is It is sealed. The material forming the battery lid 14 is, for example, the same as the material forming the battery can 11. The safety valve mechanism 15 and the PTC element 16 are provided inside the battery lid 14, and the safety valve mechanism 15 is electrically connected to the battery lid 14 via the PTC element 16. In this safety valve mechanism 15, when the internal pressure of the battery can 11 exceeds a certain level due to, for example, an internal short circuit and external heating, the disk plate 15A is inverted, so that the electrical connection between the battery lid 14 and the spirally wound electrode body 20 is reduced. The connection is broken. The electric resistance of the PTC element 16 increases with an increase in temperature in order to prevent abnormal heat generation due to a large current. The gasket 17 includes, for example, an insulating material. However, the surface of the gasket 17 may be coated with, for example, asphalt.

A center pin 24, for example, is inserted in the space 20C provided at the winding center of the spirally wound electrode body 20. However, the center pin 24 does not have to be inserted into the space 20C. A positive electrode lead 25 is connected to the positive electrode 21, and the positive electrode lead 25 contains a conductive material such as aluminum. The positive electrode lead 25 is electrically connected to the battery lid 14 via the safety valve mechanism 15, for example. A negative electrode lead 26 is connected to the negative electrode 22, and the negative electrode lead 26 contains a conductive material such as nickel. The negative electrode lead 26 is electrically connected to the battery can 11, for example.

[Positive electrode]
The positive electrode 21 includes, for example, as shown in FIG. 5, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. The positive electrode active material layer 21B may be provided, for example, on only one surface of the positive electrode current collector 21A, or may be provided on both surfaces of the positive electrode current collector 21A. In FIG. 5, for example, the case where the positive electrode active material layer 21B is provided on both surfaces of the positive electrode current collector 21A is shown.

The cathode current collector 21A contains a conductive material such as aluminum. The positive electrode active material layer 21B contains, as a positive electrode active material, any one kind or two or more kinds of positive electrode materials capable of inserting and extracting lithium. However, the positive electrode active material layer 21B may further include any one kind or two or more kinds of other materials such as a positive electrode binder and a positive electrode conductive agent.

The positive electrode material contains, for example, a lithium compound, and the lithium compound is a general term for compounds containing lithium as a constituent element. This is because a high energy density can be obtained. The type of lithium compound is not particularly limited, and examples thereof include a lithium composite oxide and a lithium phosphate compound.

The lithium composite oxide is an oxide containing lithium and one or more kinds of other elements as constituent elements, and has a crystal structure such as a layered rock salt type and a spinel type. The lithium phosphoric acid compound is a phosphoric acid compound containing lithium and one or more kinds of other elements as constituent elements, and has, for example, an olivine type crystal structure.

Other elements are elements other than lithium. The type of the other element is not particularly limited, but is preferably an element belonging to Groups 2 to 15 of the long periodic table. This is because a high voltage can be obtained. Specifically, the other element is, for example, nickel, cobalt, manganese, iron, or the like.

The lithium composite oxide having a layered rock salt type crystal structure is, for example, LiNiO ₂ , LiCoO ₂ , LiCo _0.98 Al _0.01 Mg _0.01 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , or LiNiO ₂ . _0.33 Co _0.33 Mn _0.33 O ₂ , Li _1.2 Mn _0.52 Co _0.175 Ni _0.1 O ₂ and Li _1.15 (Mn _0.65 Ni _0.22 Co _0.13 ) O ₂ and the like. The lithium composite oxide having a spinel type crystal structure is, for example, LiMn ₂ O ₄ . The lithium phosphate compound having an olivine type crystal structure is, for example, LiFePO ₄ , LiMnPO ₄ , LiMn _0.5 Fe _0.5 PO ₄ , LiMn _0.7 Fe _0.3 PO ₄ and LiMn _0.75 Fe _0.25 PO ₄ .

Details regarding each of the positive electrode binder and the negative electrode conductive agent are the same as the details regarding each of the negative electrode binder and the negative electrode conductive agent, for example.

[Negative electrode]
The negative electrode 22 has the same configuration as the negative electrode 10 described above. That is, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B, for example, as shown in FIG. The respective configurations of the negative electrode current collector 22A and the negative electrode active material layer 22B are the same as the respective configurations of the negative electrode current collector 1 and the negative electrode active material layer 2.

[Separator]
The separator 23 includes, for example, a porous film such as synthetic resin and ceramic, and may be a laminated film in which two or more kinds of porous films are laminated with each other. The synthetic resin is, for example, polyethylene.

In particular, the separator 23 may include, for example, the above-mentioned porous film (base material layer) and a polymer compound layer provided on the base material layer. The polymer compound layer may be provided on only one surface of the base material layer, or may be provided on both surfaces of the base material layer, for example. This is because the adhesion of the separator 23 to the positive electrode 21 is improved and the adhesion of the separator 23 to the negative electrode 22 is improved, so that the spirally wound electrode body 20 is less likely to be distorted. Thereby, the decomposition reaction of the electrolytic solution is suppressed, and the leakage of the electrolytic solution with which the base material layer is impregnated is also suppressed.

The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. The polymer compound layer may include a plurality of insulating particles such as inorganic particles. This is because the safety is improved. The type of inorganic particles is not particularly limited, but examples thereof include aluminum oxide and aluminum nitride.

[Electrolyte]
As described above, the electrolytic solution is impregnated in the spirally wound electrode body 20. Therefore, for example, the electrolytic solution is impregnated in the separator 23 and also in the positive electrode 21 and the negative electrode 22. This electrolytic solution contains, for example, a solvent and an electrolyte salt.

The solvent includes, for example, any one kind or two or more kinds of non-aqueous solvent (organic solvent) and the like. The electrolytic solution containing a non-aqueous solvent is a so-called non-aqueous electrolytic solution.

The type of non-aqueous solvent is not particularly limited, and examples thereof include cyclic carbonic acid ester, chain carbonic acid ester, lactone, chain carboxylic acid ester, and nitrile (mononitrile) compound. Cyclic carbonates are, for example, ethylene carbonate and propylene carbonate. The chain carbonic acid ester is, for example, dimethyl carbonate or diethyl carbonate. The lactone is, for example, γ-butyrolactone or γ-valerolactone. The chain carboxylic acid ester is, for example, methyl acetate, ethyl acetate and methyl propionate. Nitrile compounds are, for example, acetonitrile, methoxyacetonitrile and 3-methoxypropionitrile. This is because excellent battery capacity, cycle characteristics and storage characteristics can be obtained.

The non-aqueous solvent may be, for example, unsaturated cyclic carbonic acid ester, halogenated carbonic acid ester, sulfonic acid ester, acid anhydride, dicyano compound (dinitrile compound) and diisocyanate compound, phosphoric acid ester, and the like. The unsaturated cyclic carbonic acid ester is, for example, vinylene carbonate, vinyl ethylene carbonate, methylene ethylene carbonate, or the like. Examples of the halogenated carbonic acid ester include 4-fluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one and fluoromethylmethyl carbonate. Examples of the sulfonic acid ester include 1,3-propane sultone and 1,3-propene sultone. Examples of the acid anhydride include succinic anhydride, glutaric anhydride, maleic anhydride, ethanedisulfonic acid anhydride, propanedisulfonic acid anhydride, sulfobenzoic acid anhydride, sulfopropionic acid anhydride, and sulfobutyric anhydride. The dinitrile compound is, for example, succinonitrile, glutaronitrile, adiponitrile and phthalonitrile. The diisocyanate compound is, for example, hexamethylene diisocyanate. The phosphoric acid ester is, for example, trimethyl phosphate and triethyl phosphate. This is because any one type or two or more types of the series of characteristics described above are further improved.

The electrolyte salt contains, for example, one kind or two or more kinds of lithium salts and the like. The type of lithium salt is not particularly limited, and examples thereof include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), and bis (fluorosulfonyl) imide lithium (LiN (SO ₂ F) ₂ ), Lithium bis (trifluoromethanesulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ ), lithium fluorophosphate (Li ₂ PFO ₃ ), lithium difluorophosphate (LiPF ₂ O ₂ ) and lithium bis (oxalato) borate (LiC ₄ BO ₈ ) and the like. This is because excellent battery capacity, cycle characteristics and storage characteristics can be obtained.

The content of the electrolyte salt is not particularly limited, but is, for example, 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent.

<2-1-2. Operation>
In this lithium-ion secondary battery, for example, during charging, lithium ions are released from the positive electrode 21 and the lithium ions are occluded in the negative electrode 22 via the electrolytic solution. Further, in the lithium ion secondary battery, for example, during discharging, lithium ions are released from the negative electrode 22 and the lithium ions are occluded in the positive electrode 21 via the electrolytic solution.

<2-1-3. Manufacturing method>
When manufacturing a lithium ion secondary battery, for example, the positive electrode 21 is manufactured, the negative electrode 22 is manufactured, and the electrolytic solution is prepared by the procedure described below, and then the lithium ion secondary battery is assembled.

[Production of positive electrode]
First, a positive electrode active material and, if necessary, a positive electrode binder, a positive electrode conductive agent, and the like are mixed to obtain a positive electrode mixture. Then, the positive electrode mixture slurry is prepared by dispersing or dissolving the positive electrode mixture in an organic solvent or an aqueous solvent. Finally, the positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 21A, and then the positive electrode mixture slurry is dried to form the positive electrode active material layer 21B. After that, the positive electrode active material layer 21B may be compression-molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated or compression molding may be repeated a plurality of times.

[Preparation of negative electrode]
Negative electrode active material layers 22B are formed on both surfaces of the negative electrode current collector 22A by the same procedure as the above-described procedure for producing the negative electrode 20.

[Preparation of electrolyte]
After the electrolyte salt is added to the solvent, the solvent is stirred to dissolve the electrolyte salt in the solvent. In this case, the above-mentioned unsaturated cyclic carbonic acid ester and halogenated carbonic acid ester may be added as additives to the solvent.

[Assembly of lithium-ion secondary battery]
First, the positive electrode lead 25 is connected to the positive electrode current collector 21A using a welding method or the like, and the negative electrode lead 26 is connected to the negative electrode current collector 22A using a welding method or the like. Then, the positive electrode 21 and the negative electrode 22 are laminated on each other via the separator 23, and then the positive electrode 21, the negative electrode 22 and the separator 23 are wound to form a wound body. Then, the center pin 24 is inserted into the space 20C provided in the winding center of the wound body.

Next, with the wound body sandwiched by the pair of insulating

plates

12 and 13, the wound body is housed inside the battery can 11. In this case, the positive electrode lead 25 is connected to the safety valve mechanism 15 by a welding method or the like, and the negative electrode lead 26 is connected to the battery can 11 by a welding method or the like. Then, the wound body is impregnated with the electrolytic solution by injecting the electrolytic solution into the battery can 11. Thereby, the positive electrode 21, the negative electrode 22, and the separator 23 are each impregnated with the electrolytic solution, so that the wound electrode body 20 is formed.

Finally, by caulking the open end of the battery can 11 via the gasket 17, the battery lid 14, the safety valve mechanism 15, and the PTC device 16 are attached to the open end of the battery can 11. As a result, the spirally wound electrode body 20 is sealed inside the battery can 11, so that the lithium ion secondary battery is completed.

<2-1-4. Action and effect>
According to this cylindrical lithium ion secondary battery, the negative electrode 22 has the same configuration as the negative electrode 10 described above. Therefore, for the reasons described above, lithium ions are likely to smoothly and stably input and output to and from the negative electrode 22, so that excellent battery characteristics can be obtained. The other functions and effects of the cylindrical lithium ion secondary battery are similar to those of the negative electrode 10 described above.

<2-2. Laminated film type>
Next, a laminated film type lithium ion secondary battery will be described as another example of the lithium ion secondary battery. In the following description, the constituent elements of the cylindrical lithium-ion secondary battery (see FIGS. 4 and 5) that have already been described are cited as needed.

FIG. 6 shows a perspective configuration of another lithium ion secondary battery, and FIG. 7 shows a main part of the lithium ion secondary battery (rolled electrode body 30) taken along the line VII-VII shown in FIG. ) Is expanding the cross-sectional structure. However, FIG. 6 shows a state where the spirally wound electrode body 30 and the exterior member 40 are separated from each other.

<2-2-1. Composition>
In this lithium-ion secondary battery, for example, as shown in FIG. 6, a battery element (rolled electrode body 30) is housed inside a film-like exterior member 40 having flexibility (or flexibility). There is.

The wound electrode body 30 is, for example, a structure in which a positive electrode 33 and a negative electrode 34 are laminated on each other via a separator 35 and an electrolyte layer 36, and then the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte layer 36 are wound. The surface of the spirally wound electrode body 30 is protected by a protective tape 37, for example. The electrolyte layer 36 is interposed, for example, between the positive electrode 33 and the separator 35 and also between the negative electrode 34 and the separator 35.

The positive electrode lead 31 is connected to the positive electrode 33, and the positive electrode lead 31 is led out from the inside of the exterior member 40 toward the outside. The material for forming the positive electrode lead 31 is, for example, the same as the material for forming the positive electrode lead 25, and the shape of the positive electrode lead 31 is, for example, a thin plate shape or a mesh shape.

The negative electrode lead 32 is connected to the negative electrode 34, and the negative electrode lead 32 is led out from the inside of the exterior member 40 toward the outside. The derivation direction of the negative electrode lead 32 is the same as the derivation direction of the positive electrode lead 31, for example. The material forming the negative electrode lead 32 is, for example, the same as the material forming the negative electrode lead 26, and the shape of the negative electrode lead 32 is the same as the shape of the positive electrode lead 31, for example.

[Exterior member]
The exterior member 40 is, for example, a single film that can be folded in the direction of the arrow R shown in FIG. A part of the exterior member 40 is provided with a recess 40U for housing the spirally wound electrode body 30, for example.

The exterior member 40 is, for example, a laminate (laminate film) in which a fusion bonding layer, a metal layer, and a surface protection layer are laminated in this order from the inside to the outside. In the manufacturing process of the lithium-ion secondary battery, for example, after the exterior member 40 is folded so that the fusion layers face each other with the spirally wound electrode body 30 in between, the outer peripheral edge portions of the fusion layers are adjacent to each other. Are fused together. The fusing layer is, for example, a film containing a polymer compound such as polypropylene. The metal layer is, for example, a metal foil containing a metal material such as aluminum. The surface protective layer is, for example, a film containing a polymer compound such as nylon. However, the exterior member 40 is, for example, two laminated films, and the two laminated films may be bonded to each other via an adhesive, for example.

Between the exterior member 40 and the positive electrode lead 31, for example, an adhesion film 41 is inserted to prevent outside air from entering. The adhesion film 41 contains a polyolefin resin such as polypropylene.

Between the exterior member 40 and the negative electrode lead 32, for example, an adhesive film 42 having the same function as the adhesive film 41 is inserted. The forming material of the contact film 42 is, for example, the same as the forming material of the contact film 41.

[Positive electrode, negative electrode and separator]
The positive electrode 33 includes, for example, a positive electrode current collector 33A and a positive electrode active material layer 33B, and the negative electrode 34 includes, for example, a negative electrode current collector 34A and a negative electrode active material layer 34B. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, and the negative electrode active material layer 34B are, for example, the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode. The configurations are the same as those of the active material layer 22B. The configuration of the separator 35 is similar to that of the separator 23, for example.

[Electrolyte layer]
The electrolyte layer 36 contains a polymer compound together with an electrolytic solution. Since the electrolyte layer 36 described here is a so-called gel electrolyte, the electrolyte solution is held by the polymer compound in the electrolyte layer 36. This is because a high ionic conductivity (for example, 1 mS / cm or more at room temperature) is obtained, and leakage of the electrolytic solution is prevented. However, the electrolyte layer 36 may further include other materials such as various additives.

The composition of the electrolyte is as described above. The polymer compound contains, for example, one or both of a homopolymer and a copolymer. The homopolymer is, for example, polyvinylidene fluoride, and the copolymer is, for example, a copolymer of vinylidene fluoride and hexafluoropyrene.

In the electrolyte layer 36 which is a gel electrolyte, the solvent contained in the electrolytic solution is a broad concept including not only a liquid material but also a material having ion conductivity capable of dissociating an electrolyte salt. Therefore, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

<2-2-2. Operation>
In this lithium-ion secondary battery, for example, during charging, lithium ions are released from the positive electrode 33, and the lithium ions are occluded in the negative electrode 34 via the electrolyte layer 36. In the lithium-ion secondary battery, for example, during discharge, lithium ions are released from the negative electrode 34 and the lithium ions are stored in the positive electrode 33 via the electrolyte layer 36.

<2-2-3. Manufacturing method>
The lithium-ion secondary battery provided with the electrolyte layer 36 is manufactured by, for example, three types of procedures described below.

[First procedure]
First, the positive electrode 33 is manufactured by forming the positive electrode active material layers 33B on both surfaces of the positive electrode current collector 33A by a procedure similar to the procedure for manufacturing the positive electrode 21. Further, the negative electrode 34 is manufactured by forming the negative electrode active material layers 34B on both surfaces of the negative electrode current collector 34A by the same procedure as the manufacturing procedure of the negative electrode 22.

Next, after preparing the electrolytic solution, the precursor solution is prepared by mixing the electrolytic solution, the polymer compound, and the organic solvent. Subsequently, after applying the precursor solution to the positive electrode 33, the precursor solution is dried to form the electrolyte layer 36. Further, the electrolyte layer 36 is formed by applying the precursor solution to the negative electrode 34 and then drying the precursor solution. Subsequently, the positive electrode lead 31 is connected to the positive electrode current collector 33A using a welding method or the like, and the negative electrode lead 32 is connected to the negative electrode current collector 34A using a welding method or the like. Subsequently, the positive electrode 33 and the negative electrode 34 are laminated on each other via the separator 35 and the electrolyte layer 36, and then the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte layer 36 are wound to form the wound electrode body 30. Form. Then, the protective tape 37 is attached to the surface of the spirally wound electrode body 30.

Finally, after folding the exterior member 40 so as to sandwich the spirally wound electrode body 30, the outer peripheral edge portions of the exterior member 40 are adhered to each other by using a heat fusion method or the like. In this case, the adhesion film 41 is inserted between the exterior member 40 and the positive electrode lead 31, and the adhesion film 42 is inserted between the exterior member 40 and the negative electrode lead 32. As a result, the spirally wound electrode body 30 is sealed inside the exterior member 40, so that the lithium ion secondary battery is completed.

[Second procedure]
First, after the positive electrode 33 and the negative electrode 34 are manufactured, the positive electrode lead 31 is connected to the positive electrode 33 and the negative electrode lead 32 is connected to the negative electrode 34. Subsequently, the positive electrode 33 and the negative electrode 34 are laminated on each other via the separator 35, and the positive electrode 33, the negative electrode 34, and the separator 35 are wound to form a wound body. Then, the protective tape 37 is attached to the surface of the wound body. Next, after the exterior member 40 is folded so as to sandwich the wound body, the remaining outer peripheral edge portions of the exterior member 40 excluding one outer peripheral edge portion are bonded to each other by using a heat fusion method or the like. Thus, the wound body is housed inside the bag-shaped exterior member 40.

Subsequently, the electrolyte solution, the monomer that is the raw material of the polymer compound, the polymerization initiator, and if necessary, other materials such as a polymerization inhibitor are mixed, and then the mixture is stirred to prepare an electrolyte solution. A composition is prepared. Subsequently, the electrolyte composition is injected into the bag-shaped exterior member 40, and then the exterior member 40 is sealed by a heat fusion method or the like. Finally, the polymer is formed by thermally polymerizing the monomers. As a result, the electrolytic solution is held by the polymer compound, so that the electrolyte layer 36 is formed. Therefore, since the spirally wound electrode body 30 is enclosed inside the exterior member 40, the lithium ion secondary battery is completed.

[Third procedure]
First, a wound body is produced by a procedure similar to the above-described second procedure except that the separator 35 having the polymer compound layers provided on both surfaces of the base material layer is used, and then the bag-shaped exterior member. The wound body is stored inside 40. Subsequently, after the electrolytic solution is injected into the exterior member 40, the opening of the exterior member 40 is sealed by using a heat fusion method or the like. Finally, by heating the exterior member 40 while applying a load to the exterior member 40, the separator 35 is brought into close contact with each of the positive electrode 33 and the negative electrode 34 via the polymer compound layer. As a result, the polymer compound layer is impregnated with the electrolytic solution and the polymer compound layer is gelated, so that the electrolyte layer 36 is formed. Therefore, since the spirally wound electrode body 30 is enclosed inside the exterior member 40, the lithium ion secondary battery is completed.

In this third procedure, compared to the first procedure, the lithium-ion secondary battery is less likely to swell. Further, in the third procedure, as compared with the second procedure, the solvent and the monomer (raw material of the polymer compound) are less likely to remain in the electrolyte layer 36, so that the positive electrode 33, the negative electrode 34, and the separator 35 are respectively removed. The electrolyte layer 36 is sufficiently adhered.

<2-2-4. Action and effect>
According to this laminate film type lithium ion secondary battery, since the negative electrode 34 has the same configuration as the negative electrode 10 described above, it has excellent battery characteristics similar to the cylindrical lithium ion secondary battery described above. Can be obtained. The other functions and effects of the cylindrical laminated film type lithium ion secondary battery are similar to those of the cylindrical lithium ion secondary battery.

<3. Modification>
The laminate film type lithium ion secondary battery may include, for example, an electrolytic solution instead of the electrolyte layer 36. In this case, since the spirally wound electrode body 30 is impregnated with the electrolytic solution, the electrolytic solution is impregnated into each of the positive electrode 33, the negative electrode 34, and the separator 35. In addition, after the wound body is housed inside the bag-shaped exterior member 40, the electrolytic solution is injected into the bag-shaped exterior member 40, so that the wound body is impregnated with the electrolytic solution. Therefore, the wound electrode body 30 is formed. Even in this case, the same effect can be obtained.

<4. Applications of lithium-ion secondary batteries>
Applications of the above-mentioned lithium ion secondary battery are as described below, for example. However, the use of the above-mentioned negative electrode is similar to the use of the lithium-ion secondary battery, and therefore the use of the negative electrode will be described below together.

Lithium-ion secondary batteries can be used for machines, devices, appliances, devices and systems (collection of multiple devices, etc.) that can use the lithium-ion secondary battery as a power source for driving and a power storage source for power storage. It is not particularly limited as long as it is a body). The lithium ion secondary battery used as a power source may be a main power source or an auxiliary power source. The main power source is a power source that is preferentially used regardless of the presence or absence of another power source. The auxiliary power source may be, for example, a power source used instead of the main power source, or a power source that can be switched from the main power source as needed. When the lithium ion secondary battery is used as the auxiliary power source, the type of main power source is not limited to the lithium ion secondary battery.

The usage of the lithium-ion secondary battery is, for example, as follows. Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, notebook computers, cordless phones, headphone stereos, portable radios, portable televisions and portable information terminals. It is a portable household appliance such as an electric shaver. It is a storage device such as a backup power supply and a memory card. Electric tools such as electric drills and electric saws. This is a battery pack that can be mounted on a laptop computer as a detachable power source. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric vehicles (including hybrid vehicles). It is a power storage system such as a household battery system that stores power in case of an emergency. Of course, the use of the lithium ion secondary battery may be other than the above-mentioned use.

Explain an example of this technology.

(Experimental Examples 1 to 17)
As described below, after producing the laminated film type lithium ion secondary battery shown in FIGS. 6 and 7, the battery characteristics of the lithium ion secondary battery were evaluated.

[Preparation of lithium-ion secondary battery]
When manufacturing the positive electrode 33, first, 91 parts by mass of the positive electrode active material (lithium cobalt oxide (LiCoO ₂ )), 3 parts by mass of the positive electrode binder (polyvinylidene fluoride), and the positive electrode conductive material (graphite) 6 A positive electrode mixture was obtained by mixing with parts by mass. Then, the positive electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Then, the positive electrode current collector 33A (band-shaped aluminum foil, thickness = 12 μm) is coated with the positive electrode mixture slurry on both sides by using a coating device, and the positive electrode mixture slurry is dried to obtain the positive electrode active material. Layer 33B was formed. Finally, the positive electrode active material layer 33B was compression-molded using a roll press.

When manufacturing the negative electrode 34, first, an ion conductive substance (polyethylene oxide (PEO) which is an ion conductive polymer, ion conductivity = 10 ⁻⁶ S / cm) and a plurality of carbon-containing particles ( A mixture was obtained by mixing graphite) with a plurality of silicon-containing particles (silicon). The mixing ratio (% by weight) of the ion conductive material, the plurality of carbon-containing particles and the plurality of silicon-containing particles, and the weight ratios R1 and R2 (% by weight) are as shown in Table 1. Then, the mixture was put into an aqueous solvent (pure water), and then the solvent was stirred using a stirrer to prepare a mixed solution. Then, after spraying the mixed solution using a spray drying device, the mixed solution is dried (drying temperature = 150 ° C.), whereby a plurality of carbon-containing particles and a plurality of silicon-containing particles are contained in the ion conductive material. A plurality of contained first negative electrode active material particles were obtained. In this case, as shown in Table 1, the median diameter D50 (μm) of the plurality of first negative electrode active material particles was adjusted.

In addition, when producing the negative electrode 34, for comparison, except that a non-ion conductive polymer compound (carboxymethyl cellulose (CMC)) was used in place of the ion conductive polymer compound (PEO), A similar procedure was followed. In Table 1, carboxymethyl cellulose (CMC) is also shown in the column of the ion conductive substance.

Then, a plurality of first negative electrode active material particles, a plurality of second negative electrode active material particles (graphite), a negative electrode binder (polyvinylidene fluoride) 3.0 parts by mass, and a negative electrode conductive agent (carbon black) 2 A negative electrode mixture was obtained by mixing with 0.0 part by mass. The mixing ratio (% by weight) of each of the plurality of first negative electrode active material particles and each of the plurality of second negative electrode active material particles and the weight ratio R3 (% by weight) are as shown in Table 1. In this case, as shown in Table 1, the median diameter D50 (μm) of the plurality of second negative electrode active material particles was adjusted. Subsequently, the negative electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 34A (strip-shaped copper foil, thickness = 15 μm) using a coating device, and then the negative electrode mixture slurry is dried to obtain a negative electrode active material. Layer 34B was formed. Finally, the negative electrode active material layer 34B was compression-molded using a roll press.

After preparing the negative electrode 34, the corresponding pore diameter (μm) was examined using a mercury porosimeter, and the results shown in Table 2 were obtained. The details regarding the model number of the mercury porosimeter and the measurement conditions are as described above. In this case, as shown in Table 1 and Table 2, by changing the median diameter D50 of the plurality of first negative electrode active material particles and the median diameter D50 of the plurality of second negative electrode active material particles, respectively, The pore size was adjusted.

When preparing the electrolytic solution, the electrolyte salt (lithium hexafluorophosphate) was added to the solvent (ethylene carbonate and dimethyl carbonate), and then the solvent was stirred. In this case, the mixing ratio (weight ratio) of the solvent was ethylene carbonate: dimethyl carbonate = 40: 60, and the content of the electrolyte salt was 1.0 mol / kg with respect to the solvent.

When assembling a lithium ion secondary battery, first, the positive electrode lead 31 made of aluminum was welded to the positive electrode collector 33A, and the negative electrode lead 32 made of copper was welded to the negative electrode collector 34A. Then, the positive electrode 33 and the negative electrode 34 were laminated | stacked on each other through the separator 35 (microporous polyethylene film, thickness = 15 micrometers), and the laminated body was obtained. Then, after winding the laminated body, a protective tape 37 was attached to the laminated body to obtain a wound body.

Subsequently, the exterior member 40 was folded so as to sandwich the wound body, and the outer peripheral edge portions of the two sides of the exterior member 40 were heat-sealed to each other. As the exterior member 40, a surface protective layer (nylon film, thickness = 25 μm), a metal layer (aluminum foil, thickness = 40 μm), and a fusion bonding layer (polypropylene film, thickness = 30 μm) are laminated in this order. The aluminum laminated film thus prepared was used. In this case, the adhesion film 41 (polypropylene film) was inserted between the exterior member 40 and the positive electrode lead 31, and the adhesion film 42 (polypropylene film) was inserted between the exterior member 40 and the negative electrode lead 32.

Finally, the wound body is impregnated with the electrolytic solution by injecting the electrolytic solution into the exterior member 40, and then the outer peripheral edge portions of the remaining one side of the exterior member 40 in the reduced pressure environment. Heat fused. As a result, the spirally wound electrode body 30 was formed, and the spirally wound electrode body 30 was enclosed inside the exterior member 40. Thus, a laminated film type lithium ion secondary battery was completed.

[Evaluation of lithium-ion battery characteristics]
When the battery characteristics of the lithium ion secondary battery were evaluated, the results shown in Table 2 were obtained. Here, the load characteristic showing the input / output characteristic of lithium ion was investigated.

When examining the load characteristics, first, in order to stabilize the state of the lithium ion secondary battery, the lithium ion secondary battery was charged and discharged for one cycle in a normal temperature environment (temperature = 23 ° C). At the time of charging, constant current charging was performed with a current of 0.2 C until the voltage reached 4.2 V, and then constant voltage charging was performed with a current of 4.2 V until the current reached 0.05 C, and a current of 0.2 C At that time, constant current discharge was performed until the voltage reached 2.5V. Note that 0.2 C and 0.05 C are current values at which the battery capacity (theoretical capacity) is completely discharged in 5 hours and 20 hours, respectively.

Next, after charging and discharging the lithium-ion secondary battery for one cycle in the same environment, the discharge capacity at the second cycle was measured. The charging / discharging conditions were the same as when the state of the lithium ion secondary battery was stabilized.

Next, after charging and discharging the lithium-ion secondary battery for 1 cycle in the same environment, the discharge capacity at the 3rd cycle was measured. The charging / discharging conditions were the same as those in the case where the state of the lithium ion secondary battery was stabilized, except that the current during discharging was changed to 1.0 C, 1.5 C and 2.0 C, respectively. It should be noted that 1.0 C, 1.5 C and 2.0 C are current values at which the battery capacity (theoretical capacity) is completely discharged in 1 hour, 2/3 hours and 0.5 hour, respectively.

Finally, the load maintenance ratio (%) = (discharge capacity at the 3rd cycle / discharge capacity at the 2nd cycle) × 100 was calculated. In addition, each of "1.0C", "1.5C", and "2.0C" described in Table 1 represents a current value at the time of discharging in the third cycle.

[Discussion]
As shown in Table 1 and Table 2, the load retention rate greatly fluctuated according to the configuration of the negative electrode 34, more specifically, the corresponding pore diameter. Specifically, when the corresponding pore diameter is within the range of 1 μm to 3 μm (Experimental Examples 1 to 14), compared with the case where the corresponding pore diameter is outside the range of 1 μm to 3 μm (Experimental Examples 15 and 16). , The load retention rate increased without depending on the current value during discharge. The result of the increase in the load maintenance rate in this manner indicates that lithium ions are easily input and output to and from the negative electrode 34.

The following tendencies were obtained especially when the corresponding pore size was in the range of 1 μm to 3 μm. First, when the weight ratio R1 was 1.0% by weight to 2.5% by weight, a high load retention rate was obtained. Secondly, when the weight ratio R2 was 60.6% by weight to 85.9% by weight, a high load retention rate was obtained. Thirdly, the median diameter D50 of the plurality of first negative electrode active material particles is 3.5 μm to 13.0 μm, and the median diameter D50 of the plurality of second negative electrode active material particles is 7.0 μm to 20.0 μm. And a high load maintenance rate was obtained. Fourthly, when the weight ratio R3 was 10.5% by weight to 42.1% by weight, a high load retention rate was obtained.

Of course, in the case of using the ion conductive polymer compound (PEO) (Experimental example 1), as compared with the case of using the non-ion conductive polymer compound (CMC) (Experimental example 17), the discharge The load maintenance ratio increased significantly without depending on the current value.

[Summary]
From the results shown in Table 1 and Table 2, the negative electrode active material layer 34B having pores has a plurality of first negative electrode active material particles (ion conductive material, a plurality of carbon-containing particles and a plurality of silicon-containing particles) and a plurality of When the second negative electrode active material particles were included and the corresponding pore diameter was 1 μm to 3 μm, the load characteristics of the lithium ion secondary battery were improved. Therefore, excellent battery characteristics were obtained in the lithium ion secondary battery.

Although the present technology has been described above with reference to the embodiment and the example, the aspect of the present technology is not limited to the aspect described in the embodiment and the example, and thus the aspect of the present technology can be variously modified. Is.

Specifically, the cylindrical lithium ion secondary battery and the laminate film type lithium ion secondary battery have been described, but the invention is not limited to them. For example, other lithium ion secondary batteries such as a prismatic lithium ion secondary battery and a coin type lithium ion secondary battery may be used.

Also, the case where the battery element has a winding structure has been described, but the invention is not limited to this. For example, the battery element may have another structure such as a laminated structure.

Note that the effects described in the present specification are merely examples, and the effects of the present technology are not limited to the effects described in the present specification. Therefore, other effects may be obtained with the present technology.

Claims

The positive electrode,
A negative electrode active material layer having a plurality of pores, wherein the negative electrode active material layer includes a plurality of first negative electrode active material particles and a plurality of second negative electrode active material particles, the plurality of first negative electrode active material particles Each contains a plurality of carbon-containing particles and a plurality of silicon-containing particles in an ion conductive material, each of the second negative electrode active material particles contains a carbon-containing material, and the mercury infiltration into the plurality of pores. The negative electrode having a pore size range in which the volume fraction of the amount shows a peak is 1 μm or more and 3 μm or less;
A lithium-ion secondary battery including an electrolytic solution.
The ion conductive material includes at least one of an ion conductive polymer compound and a solid electrolyte,
The lithium-ion secondary battery according to claim 1.
The ionic conductivity of the ionic conductive material is 10 -6 S / cm or more and 10 -1 S / cm or less,
The lithium ion secondary battery according to claim 1 or 2.
The ratio of the weight of the ion conductive material to the weight of the first negative electrode active material particles is 1.0 wt% or more and 2.5 wt% or less,
The lithium ion secondary battery according to any one of claims 1 to 3.
The ratio of the weight of the plurality of silicon-containing particles to the total weight of the plurality of carbon-containing particles and the weight of the plurality of silicon-containing particles is 60.6% by weight or more and 85.9% by weight or less. ,
The lithium ion secondary battery according to any one of claims 1 to 4.
The median diameter D50 of the plurality of first negative electrode active material particles is 3.5 μm or more and 13.0 μm or less,
The median diameter D50 of the plurality of second negative electrode active material particles is 7.0 μm or more and 20.0 μm or less,
The lithium ion secondary battery according to any one of claims 1 to 5.
The ratio of the weight of the plurality of first negative electrode active material particles to the total weight of the plurality of first negative electrode active material particles and the weight of the plurality of second negative electrode active material particles is 10.5% by weight. Or more and 42.1% by weight or less,
The lithium ion secondary battery according to any one of claims 1 to 6.
A negative electrode active material layer having a plurality of pores,
The negative electrode active material layer includes a plurality of first negative electrode active material particles and a plurality of second negative electrode active material particles,
Each of the plurality of first negative electrode active material particles includes a plurality of carbon-containing particles and a plurality of silicon-containing particles in the ion conductive material,
Each of the second negative electrode active material particles contains a carbon-containing material,
The range of the pore diameter at which the volume fraction of the amount of infiltration of mercury into the plurality of pores shows a peak is 1 μm or more and 3 μm or less,
Negative electrode for lithium-ion secondary battery.